U.S. patent application number 13/897652 was filed with the patent office on 2013-12-19 for organic electroluminescent element.
This patent application is currently assigned to UDC IRELAND LIMITED. The applicant listed for this patent is Yuichiro Itai, Kana Morohashi, Shizunami Ri, Shin'ichiro Sonoda, Manabu Tobise. Invention is credited to Yuichiro Itai, Kana Morohashi, Shizunami Ri, Shin'ichiro Sonoda, Manabu Tobise.
Application Number | 20130334506 13/897652 |
Document ID | / |
Family ID | 49755057 |
Filed Date | 2013-12-19 |
United States Patent
Application |
20130334506 |
Kind Code |
A1 |
Tobise; Manabu ; et
al. |
December 19, 2013 |
ORGANIC ELECTROLUMINESCENT ELEMENT
Abstract
It is an object of the present invention to provide an organic
electroluminescent element with which no light extraction layer
needs to be produced separately, which has a transparent electrode
that is advantageous in terms of cost and a simple film formation
process, and which is excellent from the standpoint of light
extraction efficiency. The present invention provides an organic
electroluminescent element in which a substrate, a first electrode
adjacent to this substrate, an organic layer including at least one
organic light-emitting layer, and a second electrode adjacent to
this organic layer are formed in this order, with this organic
electroluminescent element being such that at least one of the
aforementioned electrodes is a transparent electrode which is
transparent, which contains at least one type of light scattering
particles that are transparent and that have a primary particle
size of at least 0.5 .mu.m, and which is composed of the
aforementioned light scattering particles and a component having a
refractive index equal to or higher than the refractive index of
the aforementioned organic light-emitting layer.
Inventors: |
Tobise; Manabu; (Kanagawa,
JP) ; Itai; Yuichiro; (Kanagawa, JP) ;
Morohashi; Kana; (Kanagawa, JP) ; Sonoda;
Shin'ichiro; (Kanagawa, JP) ; Ri; Shizunami;
(Kanagawa, JP) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Tobise; Manabu
Itai; Yuichiro
Morohashi; Kana
Sonoda; Shin'ichiro
Ri; Shizunami |
Kanagawa
Kanagawa
Kanagawa
Kanagawa
Kanagawa |
|
JP
JP
JP
JP
JP |
|
|
Assignee: |
UDC IRELAND LIMITED
Dublin
IE
|
Family ID: |
49755057 |
Appl. No.: |
13/897652 |
Filed: |
May 20, 2013 |
Current U.S.
Class: |
257/40 ;
257/79 |
Current CPC
Class: |
H01L 51/5212 20130101;
H01L 51/5234 20130101; H01L 2251/5369 20130101; H01L 51/5275
20130101; H01L 51/5215 20130101; H01L 51/5268 20130101; H01L
51/5206 20130101 |
Class at
Publication: |
257/40 ;
257/79 |
International
Class: |
H01L 51/52 20060101
H01L051/52 |
Foreign Application Data
Date |
Code |
Application Number |
May 30, 2012 |
JP |
2012-123189 |
Claims
1. An organic electroluminescent element in which a substrate, a
first electrode adjacent to this substrate, an organic layer
including at least one organic light-emitting layer, and a second
electrode adjacent to this organic layer are formed in this order,
wherein at least one of said electrodes is a transparent electrode
which is transparent, which contains at least one type of light
scattering particles that are transparent and have a primary
particle size of at least 0.5 .mu.m, and which is composed of said
light scattering particles and a component having a refractive
index equal to or higher than the refractive index of said organic
light-emitting layer.
2. The organic electroluminescent element according to claim 1,
wherein the component having a refractive index equal to or higher
than the refractive index of said organic light-emitting layer
contains particles with a primary particle size of 100 nm or
less.
3. The organic electroluminescent element according to claim 2,
wherein the refractive index of said particles whose primary
particle size is 100 nm or less is at least 2.0 and no more than
3.0.
4. The organic electroluminescent element according to claim 1,
wherein the component having a refractive index equal to or higher
than the refractive index of said organic light-emitting layer
contains a conductive matrix.
5. The organic electroluminescent element according to claim 4,
wherein the component having a refractive index equal to or higher
than the refractive index of said organic light-emitting layer
contains a conductive matrix and particles whose primary particle
size is 100 nm or less, and the refractive index of said particles
whose primary particle size is 100 nm or less is higher than the
refractive index of the conductive matrix.
6. The organic electroluminescent element according to claim 1,
wherein the refractive index of the component having a refractive
index equal to or higher than the refractive index of said organic
light-emitting layer is at least 1.7 and no more than 2.2.
7. The organic electroluminescent element according to claim 1,
wherein the primary particle size of said light scattering
particles is at least 0.5 .mu.m and no more than 10 .mu.m.
8. The organic electroluminescent element according to claim 1,
wherein the refractive index of said light scattering particles is
lower than the refractive index of the component having a
refractive index equal to or higher than the refractive index of
said organic light-emitting layer.
9. An organic electroluminescent element in which a substrate, a
first electrode adjacent to this substrate, an organic layer
including at least one organic light-emitting layer, and a second
electrode adjacent to this organic layer are formed in this order,
wherein at least one of said electrodes is a transparent electrode
configured from two layers, these two layers both contain a
conductive matrix, one of said two layers contains at least one
type of light scattering particles that are transparent and have a
primary particle size of at least 0.5 .mu.m and is composed of said
light scattering particles and a component having a refractive
index equal to or higher than the refractive index of said organic
light-emitting layer, and the other layer does not contain light
scattering particles and has a refractive index that is equal to or
higher than the refractive index of the organic light-emitting
layer.
10. The organic electroluminescent element according to claim 9,
wherein of said two layers, the layer that does not contain light
scattering particles is adjacent to the organic layer.
11. The organic electroluminescent element according to claim 1,
wherein either said first electrode or second electrode is a
transparent electrode, and the other electrode is a metal
electrode.
12. The organic electroluminescent element according to claim 1,
wherein said first electrode is a transparent electrode.
13. The organic electroluminescent element according to claim 1,
wherein wiring whose resistance is lower than that of said first
electrode is provided between said first electrode and substrate,
and said first electrode covers said wiring.
Description
TECHNICAL FIELD
[0001] The present invention relates to an organic
electroluminescent element characterized in that at least one
electrode is transparent, has a refractive index equal to or higher
than the refractive index of an organic light-emitting layer, and
contains at least one type of light scattering particles.
BACKGROUND ART
[0002] An organic electroluminescent element is a self-emitting
type of light-emitting device that has, on a substrate, a pair of
electrodes comprising an anode and a cathode and an organic layer
including a light-emitting layer between this pair of electrodes,
and [these elements] are expected to find use in a variety of
applications, such as displays and lighting.
[0003] In order for the light generated by the light-emitting layer
to be taken off, at least one of the anode and the cathode of the
organic electroluminescent element needs to be an electrode having
light transmission properties. Indium tin oxide (ITO) is commonly
used as an electrode having light transmission properties.
[0004] Aiming at accomplishing both extraction of light at a high
efficiency and improvement of electrical characteristics, an
organic electroluminescent element has been proposed which has an
electrode in which a first transparent conductive layer composed of
a binder and conductive nanoparticles and a second transparent
conductive layer composed of a conductive polymer are formed in
that order on a substrate surface (Patent Document 1).
[0005] Furthermore, aiming at an increase in the surface-emission
luminance of an organic electroluminescent element, an organic
electroluminescent element featuring a substrate laminated with a
scattering layer has been proposed (Patent Document 2).
RELATED ART DOCUMENTS
Patent Documents
[0006] Patent Document 1: Japanese Laid-Open Patent Application
2012-009359 [0007] Patent Document 2: WO 03/026357
SUMMARY OF THE INVENTION
Problems to be Solved by the Invention
[0008] However, the conductive nanoparticles used in Patent
Document 1 are small in size, and there is no mention of adding
micron-order particles to the electrode.
[0009] Moreover, with the scattering layer described in Patent
Document 2, the refractive index is not taken into account at all,
so there is a problem in that light extraction efficiency cannot be
expected to be improved.
[0010] It is an object of the present invention to solve the
aforementioned problems encountered in the past and to achieve the
following goal:
[0011] Specifically, it is an object of the present invention to
provide an organic electroluminescent element with which no light
extraction layer needs to be produced separately and which has a
transparent electrode [that can be formed by] a simple film
formation process and that is advantageous in terms of cost. It is
also an object of the present invention to provide an organic
electroluminescent element with which the refractive index of the
transparent electrode is adjusted higher than that of the organic
light-emitting layer and which contains light scattering particles
and is excellent from the standpoint of light extraction
efficiency.
Means for Solving the Problems
[0012] The present inventors conducted diligent investigation aimed
at solving the aforementioned problems, and [as a result]
discovered an organic electroluminescent element in which a
substrate, a first electrode adjacent to this substrate, an organic
layer including at least one organic light-emitting layer, and a
second electrode adjacent to this organic layer are formed in this
order, wherein at least one of the aforementioned electrodes is a
transparent electrode which is transparent, which contains at least
one type of light scattering particles that are transparent and
have a primary particle size of at least 0.5 .mu.m, and which is
composed of the aforementioned light scattering particles and a
component having a refractive index equal to or higher than the
refractive index of the aforementioned organic light-emitting
layer. It was discovered that the light extraction efficiency can
be improved considerably by employing an organic electroluminescent
element having this configuration.
[0013] Specifically, the means for solving the aforementioned
problems are as follows: Note that in this Specification, [the
phrase] "x to y" indicates a range that includes the numerical
values given for "x" and "y" as the minimum and maximum values,
respectively.
[0014] (1)
[0015] An organic electroluminescent element in which a substrate,
a first electrode adjacent to the substrate, an organic layer
including at least one organic light-emitting layer, and a second
electrode adjacent to the organic layer are formed in this order,
wherein at least one of the electrodes is a transparent electrode
which is transparent, which contains at least one type of light
scattering particles that are transparent and have a primary
particle size of at least 0.5 .mu.m, and which is composed of the
light scattering particles and a component having a refractive
index equal to or higher than the refractive index of the organic
light-emitting layer.
[0016] (2)
[0017] The organic electroluminescent element according to (1),
wherein the component having a refractive index equal to or higher
than the refractive index of the organic light-emitting layer
contains particles with a primary particle size of 100 nm or
less.
[0018] (3)
[0019] The organic electroluminescent element according to (2),
wherein the refractive index of the particles whose primary
particle size is 100 nm or less is at least 2.0 and no more than
3.0.
[0020] (4)
[0021] The organic electroluminescent element according to any one
of (1) to (3), wherein the component having a refractive index
equal to or higher than the refractive index of the organic
light-emitting layer contains a conductive matrix.
[0022] (5)
[0023] The organic electroluminescent element according to (4),
wherein the component having a refractive index equal to or higher
than the refractive index of the organic light-emitting layer
contains a conductive matrix and particles whose primary particle
size is 100 nm or less, and the refractive index of the particles
whose primary particle size is 100 nm or less is higher than the
refractive index of the conductive matrix.
[0024] (6)
[0025] The organic electroluminescent element according to any one
of (1) to (5), wherein the refractive index of the component having
a refractive index equal to or higher than the refractive index of
the organic light-emitting layer is at least 1.7 and no more than
2.2.
[0026] (7)
[0027] The organic electroluminescent element according to any one
of (1) to (6), wherein the primary particle size of the light
scattering particles is at least 0.5 .mu.m and no more than 10
.mu.m.
[0028] (8)
[0029] The organic electroluminescent element according to any one
of (1) to (7), wherein the refractive index of the light scattering
particles is lower than the refractive index of the component
having a refractive index equal to or higher than the refractive
index of the organic light-emitting layer.
[0030] (9)
[0031] An organic electroluminescent element in which a substrate,
a first electrode adjacent to the substrate, an organic layer
including at least one organic light-emitting layer, and a second
electrode adjacent to the organic layer are formed in this order,
wherein
[0032] at least one of the electrodes is a transparent electrode
configured from two layers, the two layers both contain a
conductive matrix, and
[0033] one of the two layers contains at least one type of light
scattering particles that are transparent and have a primary
particle size of at least 0.5 .mu.m and is composed of the light
scattering particles and a component having a refractive index
equal to or higher than the refractive index of the organic
light-emitting layer, and the other layer does not contain light
scattering particles and has a refractive index that is equal to or
higher than the refractive index of the organic light-emitting
layer.
[0034] (10)
[0035] The organic electroluminescent element according to (9),
wherein of the two layers, the layer that does not contain light
scattering particles is adjacent to the organic layer.
[0036] (11)
[0037] The organic electroluminescent element according to any one
of (1) to (10), wherein either the first electrode or the second
electrode is a transparent electrode, and the other electrode is a
metal electrode.
[0038] (12)
[0039] The organic electroluminescent element according to any one
of (1) to (11), wherein the first electrode is a transparent
electrode.
[0040] (13)
[0041] The organic electroluminescent element according to any one
of (1) to (12), wherein wiring whose resistance is lower than that
of the first electrode is provided between the first electrode and
the substrate, and the first electrode covers the wiring.
Effects of the Invention
[0042] With the present invention, it is possible to provide an
organic electroluminescent element with which no light extraction
layer needs to be produced separately and which has a transparent
electrode that is advantageous in terms of cost and [can be formed
by] a simple film formation process. It is also possible to provide
an organic electroluminescent element with which the refractive
index of the aforementioned transparent electrode is adjusted
higher than that of the organic light-emitting layer and which is
excellent from the standpoint of light extraction efficiency.
BRIEF DESCRIPTION OF THE DRAWINGS
[0043] FIG. 1 is a schematic diagram showing the organic
electroluminescent elements in Working Example 1, Working Example
4, and Comparative Example 2;
[0044] FIG. 2 is a schematic diagram showing the organic
electroluminescent element in Working Example 2;
[0045] FIG. 3 is a schematic diagram showing the organic
electroluminescent element in Working Example 3;
[0046] FIG. 4 is a schematic diagram showing the organic
electroluminescent elements in Working Examples 5 to 8;
[0047] FIG. 5 is a schematic diagram showing the organic
electroluminescent element in Comparative Example 1;
[0048] FIG. 6 is a schematic diagram showing the organic
electroluminescent element in Comparative Example 3;
[0049] FIG. 7 is a schematic diagram showing the organic
electroluminescent element in Comparative Example 4;
[0050] FIG. 8 is a schematic diagram showing the organic
electroluminescent element in Comparative Example 5; and
[0051] FIG. 9 is a schematic diagram showing the organic
electroluminescent element in Comparative Example 0.
DETAILED DESCRIPTION OF EMBODIMENTS
[0052] The organic electroluminescent element of the present
invention is an organic electroluminescent element in which a
substrate, a first electrode adjacent to this substrate, an organic
layer including at least one organic light-emitting layer, and a
second electrode adjacent to this organic layer are formed in this
order, with at least one of the aforementioned electrodes including
a transparent electrode which is transparent, which contains at
least one type of light scattering particles that are transparent
and have a primary particle size of at least 0.5 .mu.m, and which
is composed of the aforementioned light scattering particles and a
component having a refractive index equal to or higher than the
refractive index of the aforementioned organic light-emitting
layer.
[0053] (Electrodes)
[0054] At least one of the first electrode and second electrode of
the present invention is a transparent electrode (hereinafter also
referred to as a "conductive layer" or a "coating-type diffused
conductive layer") which is transparent, which contains at least
one type of light scattering particles that are transparent and
have a primary particle size of at least 0.5 .mu.m, and which is
composed of the aforementioned light scattering particles and a
component having a refractive index equal to or higher than the
refractive index of the aforementioned organic light-emitting
layer.
[0055] There are no particular restrictions on the conductive layer
included in the organic electroluminescent element of the present
invention as long as it is transparent and composed of the
aforementioned light scattering particles and a component having a
refractive index that is equal to or higher than the refractive
index of the aforementioned organic light-emitting layer, and it
can be formed by light scattering particles and a conductive
matrix, for example.
[0056] Here, the primary particle size of the light scattering
particles in this Specification is a primary particle size [found
by] dispersing 1 g of light scattering particles in 200 g of
methanol, measuring the size of the light scattering particles
using a "Multisizer II" precision particle size distribution
measurement device made by Peckman Coulter [sic].sup.1, and
calculating so as to obtain an average particle size by volumetric
standard. .sup.1Translator's note: "Peckman Coulter" is likely a
typological error in the original for "Beckman Coulter."
[0057] Furthermore, saying that the conductive layer is transparent
means that the absorbency (A(.lamda.)) found using the following
equation from the amount of incident light (I.sub.0) and the total
value of the amount of transmitted light (I.sub.T) including the
transmitted and scattered component and the amount of reflected
light (I.sub.R) including the scattered and reflected light, in the
visible light region, and particularly over the range of
wavelengths of 450 to 750 nm, is 1 or less.
A(.lamda.)=-log.sub.10 {(I.sub.T+I.sub.R)/I.sub.0}
[0058] The "transparent conductive layer" in the present invention
also encompasses, for example, inorganic conductive oxide materials
such as ITO or conductive polymer materials such as PEDOT-PSS.
[0059] From the standpoint of a balance between optical
transmissivity and resistance, the thickness of the conductive
layer is preferably at least 100 nm and no more than 10 .mu.m, more
preferably at least 100 nm and no more than 7 .mu.m, and even more
preferably at least 100 nm and no more than 5 .mu.m.
[0060] The average thickness of the conductive layer can be found,
for example, by cutting out part of the conductive layer and
measuring it with a scanning electron microscope (S-3400N, made by
Hitachi High-Technologies Corporation).
[0061] (Light Scattering Particles)
[0062] There are no particular restrictions on the light scattering
particles as long as the primary particle size is at least 0.5
.mu.m, and the particles are capable of scattering or diffusing
light. [The particles] can be suitably selected according to their
intended use and may be either organic or inorganic particles, and
two or more types of particle may be contained.
[0063] Examples of the aforementioned organic particles include
polymethyl methacrylate particles, crosslinked polymethyl
methacrylate particles, acrylic-styrene copolymer particles,
melamine particles, polycarbonate particles, polystyrene particles,
crosslinked polystyrene particles, polyvinyl chloride particles,
and benzoguanamine-melamine formaldehyde particles.
[0064] Examples of the aforementioned inorganic particles include
ZrO.sub.2, TiO.sub.2, Al.sub.2O.sub.3, In.sub.2O.sub.3, ZnO,
SnO.sub.2, and Sb.sub.2O.sub.3. Of these, TiO.sub.2, ZrO.sub.2,
ZnO, and SnO.sub.2 are particularly favorable.
[0065] Of these, in terms of dispersibility in a binder and solvent
resistance, the aforementioned light scattering particles are
preferably resin particles in a crosslinked state, with crosslinked
polymethyl methacrylate particles being particularly favorable.
[0066] It can be confirmed that the aforementioned light scattering
particles are resin particles in a crosslinked state by dispersing
the resin particles in a solvent, e.g., toluene, and checking to
see how difficult it is for them to dissolve.
[0067] There are no particular restrictions on the refractive index
of the light scattering particles, which can be suitably selected
according to the intended use, but it is preferably at least 1.0
and no more than 3.0, more preferably at least 1.2 and no more than
2.0, and even more preferably at least 1.3 and no more than 1.7. If
the aforementioned refractive index is at least 1.0 and no more
than 3.0, light diffusion (scattering) will not be excessive, so
the light extraction efficiency will tend to be better.
[0068] Moreover, the refractive index of the light scattering
particles is preferably lower than the refractive index of the
component having a refractive index equal to or higher than the
refractive index of the aforementioned organic light-emitting
layer.
[0069] Note that, in this Specification, "the refractive index of
the component having a refractive index equal to or higher than the
refractive index of the aforementioned organic light-emitting
layer" refers to the refractive index of the product of removing
the light scattering particles from the entire component
constituting the conductive layer (refractive index control
particles, conductive matrix, etc.).
[0070] The reason for removing the refractive index of the light
scattering particles in evaluating the refractive index of the
conductive layer is that the light scattering particles are
sufficiently larger than the wavelength of the light, and the
refractive index of the light scattering particles has almost no
effect on changes in the light extraction efficiency attributable
to the relationship between the magnitude of the refractive index
of the organic light-emitting layer and the magnitude of the
refractive index of the conductive layer. The aforementioned
"refractive index of the component having a refractive index equal
to or higher than the refractive index of the organic
light-emitting layer" will hereinafter also be referred to simply
as "the refractive index of the conductive layer" in some
instances.
[0071] The refractive index of the conductive layer was measured by
forming, on a silicon substrate or a quartz substrate, a film of
the component having a refractive index equal to or higher than the
refractive index of the aforementioned organic light-emitting layer
in a thickness approximately corresponding to the wavelength of the
light and measuring the refractive index of the film thus formed on
the substrate with an ellipsometer.
[0072] In addition, the refractive index of the light scattering
particles in this Specification is a refractive index which was
measured by an ellipsometer used for measuring a refractive index
for the aforementioned conductive layer obtained by using the raw
material of the aforementioned light scattering particles to form a
film on a silicon substrate in a thickness approximately
corresponding to the wavelength of the light source of the
aforementioned ellipsometer. The refractive index of the particles
with a primary particle size of 100 nm or less (described later) is
also measured in the same manner.
[0073] The primary particle size of the aforementioned light
scattering particles is preferably at least 0.5 .mu.m and no more
than 10 .mu.m, more preferably at least 0.5 .mu.m and no more than
6 .mu.m, and even more preferably at least 1 .mu.m and no more than
3 .mu.m. If the primary particle size of the aforementioned light
scattering particles is 10 .mu.m or less, light will tend not to be
scattered forward, so the light scattering particles will tend not
to decrease the ability to change the angle of the light.
[0074] On the other hand, if the primary particle size of the
aforementioned light scattering particles is less than 0.5 .mu.m,
they will be smaller than the wavelength of visible light, and Mie
scattering will change to the region of Rayleigh scattering.
Consequently, the wavelength dependence of scattering efficiency of
the light scattering particles will increase, and the chromaticity
of the organic electroluminescent device will be prone to changing,
which is undesirable. This is also undesirable in that rearward
scattering will be so strong that light extraction efficiency will
end up decreasing.
[0075] The amount in which the light scattering particles are
contained in the conductive layer is preferably at least 30 vol %
and no more than 66 vol %, more preferably at least 30 vol % and no
more than 60 vol %, and even more preferably at least 30 vol % and
no more than 55 vol %. If the aforementioned amount is at least 30
vol %, there will be a higher probability that light incident on
the conductive layer will be scattered by the light scattering
particles, and the ability to change the light angle of the
conductive layer will be greater, so light extraction efficiency
will increase even though the thickness of the conductive layer is
not increased. This is also linked to a decrease in cost since the
thickness of the aforementioned conductive layer need not be
increased, and there will be less variance in the thickness of the
conductive layer, making it less likely that there will be variance
in the scattering effect within the light emission face. On the
other hand, if the aforementioned amount is 66 vol % or less, the
surface of the aforementioned conductive layer will not be too
rough, and voids will tend not to be produced internally, so there
is less likely to be a decrease in the physical strength of the
aforementioned conductive layer.
[0076] From the standpoint of light extraction efficiency, the
conductive layer preferably includes the aforementioned resin
particles and titanium oxide microparticles that have undergone
photocatalytic deactivation processing. Concrete examples and the
preferable range of these titanium oxide microparticles that have
undergone photocatalytic deactivation processing are the same as
those described for the aforementioned conductive layer.
[0077] (Component Having a Refractive Index Equal to or Higher than
the Refractive Index of the Organic Light-Emitting Layer)
[0078] The conductive layer of the present invention contains a
component having a refractive index equal to or higher than the
refractive index of the organic light-emitting layer.
[0079] The "component having a refractive index equal to or higher
than the refractive index of the organic light-emitting layer" is
defined as being a component obtained by removing light scattering
particles from the component contained in the conductive layer.
Furthermore, when the conductive layer is configured from two
layers, the component having a refractive index equal to or higher
than the refractive index of the organic light-emitting layer is
defined as being, in one of the aforementioned two layers that
contains light scattering particles, a component obtained by
removing light scattering particles from the component contained in
this one layer.
[0080] The component having a refractive index equal to or higher
than the refractive index of the organic light-emitting layer may
be made up of just one component, or may be made up of two or more
components.
[0081] The component having a refractive index equal to or higher
than the refractive index of the organic light-emitting layer
preferably contains a conductive matrix and particles with a
primary particle size of 100 nm or less (described later).
[0082] For example, when the conductive layer contains light
scattering particles, a conductive matrix, and particles with a
primary particle size of 100 nm or less, the component having a
refractive index equal to or higher than the refractive index of
the organic light-emitting layer refers to a component composed of
the aforementioned conductive matrix and the aforementioned
particles with a primary particle size of 100 nm or less. Moreover,
in a conductive layer configured from two layers, if one of the
aforementioned two layers contains light scattering particles, a
conductive matrix, and particles with a primary particle size of
100 nm or less, for example, the component having a refractive
index equal to or higher than the refractive index of the organic
light-emitting layer refers to a component composed of the
aforementioned conductive matrix and the aforementioned particles
with a primary particle size of 100 nm or less.
[0083] (Particles with a Primary Particle Size of 100 nm or
Less)
[0084] In the present invention, the component having a refractive
index equal to or higher than the refractive index of the organic
light-emitting layer can contain particles with a primary particle
size of 100 nm or less (hereinafter also referred to as "nano-sized
particles" or "refractive index control particles").
[0085] The primary particle size of the nano-sized particles in
this Specification is defined as being a primary particle size
obtained by measuring the size of nano-sized particles using a
"Delsa.TM. Nano C" made by Peckman Coulter [sic].sup.2 and
performing calculation so as to obtain an average particle size by
volumetric standard. .sup.2Translator's note: "Peckman Coulter" is
likely a typological error in the original for "Beckman
Coulter."
[0086] --Nano-Sized Particles Having Refractive Index Greater than
that of Conductive Matrix--
[0087] The aforementioned nano-sized particles preferably have a
refractive index that is higher (greater) than that of the
conductive matrix (described later).
[0088] The nano-sized particles that have a refractive index
greater than that of the conductive matrix are preferably inorganic
microparticles, and are preferably metal oxide microparticles such
as microparticles of an oxide of aluminum, titanium, zirconium, or
antimony, and from the standpoint of refractive index, titanium
oxide microparticles are particularly favorable. The titanium oxide
microparticles are preferably ones that have undergone processing
to deactivate a photocatalytic effect.
[0089] ----Titanium Oxide Microparticles that have Undergone
Photocatalytic Deactivation Processing----
[0090] There are no particular restrictions on the titanium oxide
microparticles that have undergone photocatalytic deactivation
processing as long as there is no photocatalytic activity, and
[these particles] can be suitably selected according to their
intended use, but examples include (1) titanium oxide
microparticles whose surface has been covered with at least one of
alumina, silica, and zirconia, and (2) titanium oxide
microparticles produced by using a resin to cover the covered
surface of the titanium oxide microparticles obtained as in (1)
above. Examples of this resin include polymethyl methacrylate
(PMMA).
[0091] It can be confirmed that the aforementioned titanium oxide
microparticles that have undergone photocatalytic deactivation
processing have no photocatalytic activity by a methylene blue
method, for example.
[0092] There are no particular restrictions on the titanium oxide
microparticles used in the aforementioned titanium oxide
microparticles that have undergone photocatalytic deactivation
processing, which can be suitably selected according to their
intended use, but the aforementioned crystal structure is
preferably one in which rutile, a rutile/anatase mixed crystal, or
anatase is the main component, and a rutile structure is
particularly favorable as the main component.
[0093] The aforementioned titanium oxide microparticles may be
compounded by adding a metal oxide other than titanium oxide.
[0094] The metal oxide that can be compounded with the
aforementioned titanium oxide microparticles is preferably at least
one type of metal oxide selected from among tin, zirconium,
silicon, zinc, and aluminum.
[0095] The amount in which the aforementioned metal oxide is added
to titanium is preferably 1 to 40 mol %, more preferably 2 to 35
mol %, and even more preferably 3 to 30 mol %.
[0096] The primary particle size of the nano-sized particles having
a refractive index greater than that of the conductive matrix is
preferably at least 1 nm and no more than 100 nm, more preferably
at least 1 nm and no more than 30 nm, particularly preferably at
least 1 nm and no more than 25 nm, and most preferably at least 1
nm and no more than 20 nm. It is preferable for the primary
particle size to be 100 nm or less because the dispersion will tend
not to be turbid, and settling will tend not to occur, and it is
preferable for the size to be at least 1 nm because the crystal
structure will be well defined and not amorphous, and there will be
fewer changes such as gelling over time.
[0097] There are no particular restrictions on the shape of the
nano-sized particles having a refractive index greater than that of
the conductive matrix, which can be suitably selected according to
the intended use, but favorable examples include a shape like a
grain of rice, spherical, cuboid, spindle shaped, and irregular.
For the aforementioned titanium oxide microparticles, just one type
may be used alone, or two or more types may be used together.
[0098] In order to raise the refractive index of the conductive
layer, the nano-sized particles having a refractive index greater
than that of the conductive matrix preferably have a refractive
index of at least 2.0 and no more than 3.0, more preferably at
least 2.2 and no more than 3.0, even more preferably at least 2.2
and no more than 2.8, and particularly preferably at least 2.2 and
no more than 2.6. It is preferable for the aforementioned
refractive index to be at least 2.0 because the refractive index of
the conductive layer can be effectively raised, and it is
preferable for the aforementioned refractive index to be no more
than 3.0 because there will be no discoloration of the particles or
other such problems.
[0099] The refractive index of the nano-sized particles having a
refractive index greater than that of the conductive matrix can be
measured as follows: A resin material having a known refractive
index is doped with particles having a refractive index greater
than that of the conductive matrix, and the resin material in which
these particles have been dispersed is formed as a coating film
over a silicon substrate or a quartz substrate. The refractive
index of this coating film is measured with an ellipsometer, and
the refractive index of the aforementioned particles is found from
the volume fraction of the aforementioned particles and the resin
material constituting the aforementioned coating film.
[0100] Because of the need to raise the refractive index of the
aforementioned conductive layer above the refractive index of the
organic layer (and particularly the light-emitting layer), it is
preferable for the nano-sized particles having a refractive index
greater than that of the conductive matrix to be contained in the
conductive layer in an amount of at least 10 vol % and no more than
50 vol %, more preferably at least 15 vol % and no more than 50 vol
%, and even more preferably at least 20 vol % and no more than 50
vol %, with respect to the entire volume of the conductive layer.
It is preferable for this content to be at least 10 vol % because
the refractive index of the conductive layer can be effectively
raised, and the light extraction effect can be improved, and it is
preferable for the aforementioned content to be no more than 50 vol
% because Rayleigh scattering will not be strong, and the light
extraction effect can be improved.
[0101] In the present invention, from the standpoint of increasing
light extraction efficiency, the refractive index of the component
having a refractive index equal to or higher than the refractive
index of the organic light-emitting layer (the refractive index of
the conductive layer) is equal to or higher than the refractive
index of the organic light-emitting layer of the organic
electroluminescent element, and in concrete terms, it is preferably
at least 1.7 and no more than 2.2, more preferably at least 1.7 and
no more than 2.1, and even more preferably at least 1.7 and no more
than 2.0.
[0102] The resistance of the conductive layer is preferably at
least 1.OMEGA./.quadrature. (.OMEGA./sq.) and no more than
1000.OMEGA./.quadrature., more preferably at least
1.OMEGA./.quadrature. and no more than 500.OMEGA./.quadrature., and
even more preferably at least 1.OMEGA./.quadrature. and no more
than 300.OMEGA./.quadrature..
[0103] The absorbency of the conductive layer, which is expressed
by A(.lamda.) above, is preferably at least 0.001 and no more than
1, more preferably at least 0.001 and no more than 0.5, and even
more preferably at least 0.001 and no more than 0.1.
[0104] (Conductive Matrix)
[0105] The component having a refractive index equal to or higher
than that of the organic light-emitting layer of the present
invention preferably contains a conductive matrix. The conductive
matrix is preferably a conductive polymer.
[0106] The conductive polymer is preferably a .pi.-conjugated
conductive polymer or a .sigma.-conjugated conductive polymer and
more preferably a .pi.-conjugated conductive polymer.
[0107] Examples of .sigma.-conjugated conductive polymers include
poly(methylphenylsilane), poly(methylpropylsilane),
poly(phenyl-p-biphenylsilane), and poly(dihexylsilane).
[0108] --.pi.-Conjugated Conductive Polymer--
[0109] There are no particular restrictions on the .pi.-conjugated
conductive polymer as long as it is an organic polymer whose main
chain is constituted by a .pi.-conjugated system. The
.pi.-conjugated conductive polymer is preferably a .pi.-conjugated
heterocyclic compound or a derivative of a .pi.-conjugated
heterocyclic compound because of the stability of the compounds and
high conductivity.
[0110] Examples of .pi.-conjugated conductive polymers include at
least one type selected from the group composed of aliphatic
conjugated polyacetylene, polyacene, and polyazulene, aromatic
conjugated polyphenylene, heterocyclic conjugated polypyrrole,
polythiophene, and polyisothianaphthene, heteroatom-containing
conjugated polyaniline and polythienylenevinylene, mixed-type
conjugated poly(phenylenevinylene), a double chain conjugated
system which is a conjugated system having a plurality of conjugate
chains in a molecule, derivatives of these conductive polymers, and
conductive complexes which are polymers obtained by grafting or
block-copolymerization of these conjugate polymer chains to a
saturated polymer
[0111] From the standpoint of stability in air, polypyrrole,
polythiophene, polyaniline, and derivatives of these are
preferable, and polythiophene, polyaniline, and derivatives of
these (specifically, polythiophene, polyaniline, polythiophene
derivatives, and polyaniline derivatives) are more preferable.
[0112] Even an unsubstituted .pi.-conjugated conductive polymer can
have sufficient conductivity and miscibility in the binder resin,
but in order to enhance conductivity and miscibility, a functional
group such as an alkyl group, a carboxy group, a sulfo group, an
alkoxy group, or a hydroxy group is preferably introduced into the
.pi.-conjugated conductive polymer.
[0113] Concrete examples of .pi.-conjugated conductive polymers
include:
[0114] polypyrroles: polypyrrole, poly(N-methylpyrrole),
poly(3-methylpyrrole), poly(3-ethylpyrrole),
poly(3-n-propylpyrrole), poly(3-butylpyrrole),
poly(3-octylpyrrole), poly(3-decylpyrrole), poly(3-dodecylpyrrole),
poly(3,4-dimethylpyrrole), poly(3,4-dibutylpyrrole),
poly(3-carboxypyrrole), poly(3-methyl-4-carboxypyrrole),
poly(3-methyl-4-carboxyethylpyrrole),
poly(3-methyl-4-carboxybutylpyrrole), poly(3-hydroxypyrrole),
poly(3-methoxypyrrole), poly(3-ethoxypyrrole),
poly(3-butoxypyrrole), and poly(3-methyl-4-hexyloxypyrrole);
[0115] polythiophenes: poly(thiophene), poly(3-methylthiophene),
poly(3-ethylthiophene), poly(3-propylthiophene),
poly(3-butylthiophene), poly(3-hexylthiophene),
poly(3-heptylthiophene), poly(3-octylthiophene),
poly(3-decylthiophene), poly(3-dodecylthiophene),
poly(3-octadecylthiophene), poly(3-bromothiophene),
poly(3-chlorothiophene), poly(3-iodothiophene),
poly(3-cyanothiophene), poly(3-phenylthiophene),
poly(3,4-dimethylthiophene), poly(3,4-dibutylthiophene),
poly(3-hydroxythiophene), poly(3-methoxythiophene),
poly(3-ethoxythiophene), poly(3-butoxythiophene),
poly(3-hexyloxythiophene), poly(3-heptyloxythiophene),
poly(3-octyloxythiophene), poly(3-decyloxythiophene),
poly(3-dodecyloxythiophene), poly(3-octadecyloxythiophene),
poly(3-methyl-4-methoxythiophene),
poly(3,4-ethylenedioxythiophene), poly(3-methyl-4-ethoxythiophene),
poly(3-carboxythiophene), poly(3-methyl-4-carboxythiophene),
poly(3-methyl-4-carboxyethylthiophene), and
poly(3-methyl-4-carboxybutylthiophene); and
[0116] polyanilines: polyaniline, poly(2-methylaniline),
poly(3-isobutylaniline), poly(2-anilinesulfonic acid), and
poly(3-anilinesulfonic acid).
[0117] --Polymer Dopant Having an Anionic Group--
[0118] It is preferable for the .pi.-conjugated conductive polymer
to be used along with a polymer dopant having an anionic group
(also called a "polyanion dopant"). Specifically, in this case, the
result is an organic conductive polymer composition that includes
an organic conductive polymer compound (a .pi.-conjugated
conductive polymer) and a polymer dopant having an anionic group.
The use of a .pi.-conjugated conductive polymer in combination with
a polymer dopant having an anionic group increases the
conductivity, improves the stability of this conductivity over
time, and improves water resistance in a laminate state.
[0119] Examples of polyanion dopants include polymers which have
the structure of at least one of a substituted or unsubstituted
polyalkylene, a substituted or unsubstituted polyalkenylene, a
substituted or unsubstituted polyimide, a substituted or
unsubstituted polyamide, and a substituted or unsubstituted
polyester, and which include structural units having an anionic
group.
[0120] Examples of the anionic group of the polyanion dopant
include --O--SO.sub.3.sup.-X.sup.+, --SO.sub.3X.sup.+, and
--COO.sup.-X.sup.+ (in each formula, X.sup.+ represents a hydrogen
ion or an alkali metal ion).
[0121] Of these, --SO.sub.3X.sup.+ and --COO.sup.-X.sup.+ are
preferable from the standpoint of doping performance in an organic
conductive polymer compound.
[0122] Of the aforementioned polyanion dopants, from the standpoint
of solvent solubility and conductivity, preferable examples include
polyisoprenesulfonic acid, a copolymer including
polyisoprenesulfonic acid, polysulfoethyl methacrylate, a copolymer
including polysulfoethyl methacrylate, poly(4-sulfobutyl
methacrylate), a copolymer including poly(4-sulfobutyl
methacrylate), polymethallyloxybenzenesulfonic acid, a copolymer
including polymethallyloxybenzenesulfonic acid, polystyrenesulfonic
acid, and a copolymer including polystyrenesulfonic acid.
[0123] A range of monomer units of 10 to 100,000 is preferable for
the degree of polymerization of the polyanion dopant, and a range
of 50 to 10,000 is more preferable from the standpoint of solvent
solubility and conductivity.
[0124] The amount in which the polyanion dopant is contained is
preferably in the range of 0.1 to 10 mol per mole of the organic
conductive polymer compound, and more preferably in the range of 1
to 7 mol. The molar number here is defined by the number of
structural units deriving from the monomer including an anionic
group that forms the polyanion dopant and the number of structural
units deriving from the monomer such as pyrrole, thiophene, or
aniline that forms the organic conductive polymer compound. If the
polyanion dopant content is at least 0.1 mol per mole of the
organic conductive polymer compound, the doping effect to the
organic conductive polymer compound will be higher, and sufficient
conductivity will be exhibited. In addition, dispersibility and
solubility in a solvent are better, and a uniform dispersion can
easily be obtained. Furthermore, if the polyanion dopant content is
10 mol or less per mole of the organic conductive polymer compound,
a large amount of the organic conductive polymer compound can be
contained, and sufficient conductivity can easily be obtained.
[0125] --Solubility in Organic Solvent or Water--
[0126] From the standpoint of coatability, the conductive polymer
is preferably soluble in an organic solvent or water. In more
concrete terms, the conductive polymer is preferably soluble in an
amount of at least 1.0 wt % in water or an organic solvent having a
water content of 5 wt % or less and a dielectric constant of 2 to
30. [The term] "soluble" here means that [the polymer] will
dissolve in the solvent in a single molecular state or in a state
in which a plurality of single molecules are associated, or [the
polymer] will disperse in a particulate state at a particle size of
300 nm or less.
[0127] In general, organic conductive polymers have high
hydrophilicity and dissolve in water or solvents containing water
as their main component. Examples of methods for making such an
organic conductive polymer soluble in an organic solvent include
adding a compound that raises affinity with organic solvents to a
composition containing the organic conductive polymer, or adding a
dispersant in an organic solvent. Moreover, when an organic
conductive polymer and a polyanion dopant are used, it is
preferable for the polyanion dopant to undergo a hydrophobization
treatment.
[0128] Favorable organic solvents include, for example, alcohols,
aromatic hydrocarbons, ethers, ketones, and esters.
[0129] The conductive layer can be produced by coating a
transparent substrate with the various types of material discussed
above by a publicly known thin film formation method such as dip
coating, air knife coating, curtain coating, roller coating, wire
bar coating, gravure coating, micro gravure coating, or extrusion
coating, and then drying and irradiating [the film] with light
and/or heat. Preferably, curing by irradiation with light is
advantageous in terms of quick curing. Furthermore, after the
photosetting treatment, it is also preferable to perform a heat
treatment after stopping the curing of the diffused layer
(polymerization reaction) brought about by a photopolymerization
initiator. In this case, the heating temperature is preferably 60
to 105.degree. C., more preferably 70 to 100.degree. C., and even
more preferably 70 to 90.degree. C.
[0130] Any light source may be used for the optical irradiation as
long as it is near the wavelength (absorption wavelength) at which
the photopolymerization initiator reacts. When the absorption
wavelength is in the ultraviolet band, examples of light sources
include various mercury vapor lamps of low, medium, high, or
ultra-high pressure, chemical lamps, carbon arc lamps, metal halide
lamps, xenon lamps, and sunlight. Various kinds of laser light
source that can provide wavelengths from 350 to 420 nm may also be
converted for multibeam irradiation. In addition, when the
absorption wavelength is in the infrared band, examples of light
sources include halogen lamps, xenon lamps, and high-pressure
sodium lamps, and various kinds of laser light source that can
provide wavelengths from 750 to 1400 nm may also be converted for
multibeam irradiation.
[0131] In the case of radical photopolymerization by optical
irradiation, it can be performed in air or an inert gas, but using
an atmosphere containing as little oxygen as possible is preferable
in order to shorten the induction period of polymerization of a
radical polymerizable monomer, to sufficiently raise the
polymerization rate, and the like. The aforementioned oxygen
concentration range is preferably 0 to 1000 ppm, more preferably 0
to 800 ppm, and even more preferably 0 to 600 ppm. The intensity of
the irradiating UV rays is preferably 0.1 to 100 mW/cm.sup.2, and
the amount of optical irradiation on the coating film surface is
preferably 100 to 10,000 mJ/cm.sup.2, more preferably 100 to 5000
mJ/cm.sup.2, and particularly preferably 100 to 1000 mJ/cm.sup.2.
If the aforementioned amount of optical irradiation is less than
100 mJ/cm.sup.2, the conductive layer will not cure adequately and
may crumble during washing of the substrate or dissolve during
application of other coating layers over the conductive layer. On
the other hand, if the aforementioned amount of optical irradiation
exceeds 10,000 mJ/cm.sup.2, polymerization of the conductive layer
may proceed too far, causing the surface to yellow, the
transmissivity to decrease, and the light extraction efficiency to
decrease in some cases. Furthermore, the temperature in the optical
irradiation step is preferably 15 to 70.degree. C., more preferably
20 to 60.degree. C., and particularly preferably 25 to 50.degree.
C. If this temperature is lower than 15.degree. C., curing of the
conductive layer by photopolymerization may take a long time, but
if 70.degree. C. is exceeded, this may affect the
photopolymerization initiator itself, making photopolymerization
(curing) impossible in some cases.
[0132] (Substrate)
[0133] The substrate in the organic electroluminescent element of
the present invention is preferably a transparent substrate.
[0134] There are no particular restrictions on the shape,
structure, size, material, and so forth of the aforementioned
transparent substrate, which can be suitably selected according to
the intended use, but an example of the aforementioned shape is a
flat shape, the aforementioned structure may be a single-layer
structure or a laminated structure, and the aforementioned size can
be selected as appropriate.
[0135] There are no particular restrictions on the material of the
aforementioned substrate, which can be suitably selected according
to the intended use; examples include yttria-stabilized zirconia
(YSZ), glass (such as alkali-free glass and soda-lime glass), and
other such inorganic materials; polyethylene terephthalate (PET),
polyethylene naphthalate (PEN), and other such polyester resins;
polycarbonate, polyimide resins (PI), polyethylene, polyvinyl
chloride, polyvinylidene chloride, polystyrene, and
styrene-acrylonitrile copolymers. These may be used singly, or two
or more types may be used together. Of these, a polyester resin is
preferable, and from the standpoint of suitability to roll coating,
polyethylene terephthalate (PET) and polyethylene naphthalate (PEN)
are particularly preferable.
[0136] The surface of the aforementioned substrate is preferably
subjected to a surface activation treatment to improve adhesion
with the conductive layer provided over this surface. Examples of
this surface activation treatment include glow discharge treatment,
corona discharge treatment, silane coupling treatment of the glass
substrate, and so forth.
[0137] The aforementioned substrate may be produced as needed, or a
commercially available product may be used.
[0138] There are no particular restrictions on the thickness of the
aforementioned substrate, which can be suitably selected according
to the intended use, [but] it is preferably at least 10 .mu.m and
more preferably at least 50 .mu.m.
[0139] The refractive index of the aforementioned substrate is
preferably at least 1.3 and no more than 1.8, more preferably at
least 1.4 and no more than 1.7, and even more preferably at least
1.4 and no more than 1.6. If the refractive index of the
aforementioned substrate is at least 1.3, the difference in the
refractive index will not be too large between the substrate and
the conductive layer, and when light from the conductive layer is
incident [on the substrate], Fresnel reflection will not be too
strong, making it easier to increase light extraction efficiency.
If the refractive index of the aforementioned substrate is no more
than 1.8, the difference in the refractive index will not be too
large between the substrate and the air (the light emission side),
and Fresnel reflection will not be too strong, making it easier to
increase light extraction efficiency.
[0140] (Configuration of Conductive Layer)
[0141] The conductive layer in the present invention may be
configured of a single layer or a plurality of layers. If the
conductive layer is configured of a plurality of layers, from the
standpoints of ensuring flatness and also adjusting the diffusion
effect, the conductive layer is preferably configured from two
layers.
[0142] In cases where the conductive layer is configured from two
layers, it is preferable for the two layers to be composed of a
layer that contains light scattering particles and a layer that
does not contain light scattering particles and for the layer that
does not contain light scattering particles to be on the organic
layer side. Putting the layer that does not contain light
scattering particles on the organic layer side is preferable in
terms of ensuring flatness of the surface of the conductive layer
on the side that is in contact with the organic layer and
eliminating the risk of electrical leakage within the organic layer
caused by unevenness of the conductive layer, as well as the
decrease in light extraction efficiency that would be attendant on
this leakage. The electrical leakage referred to in this
Specification indicates the leakage of current, for example.
[0143] Moreover, from the standpoints of adhesion between the two
layers constituting the conductive layer and reducing reflection
caused by a difference in refractive index, the layer that contains
light scattering particles is preferably such that the components
other than light scattering particles are the same as those in the
layer that does not contain light scattering particles.
[0144] In addition, the organic electroluminescent element in the
present invention is an organic electroluminescent element in which
a substrate, a first electrode adjacent to this substrate, an
organic layer including at least one organic light-emitting layer,
and a second electrode adjacent to this organic layer are formed in
this order, with this organic electroluminescent element being
preferably such that at least one of the aforementioned electrodes
is a transparent electrode configured from two layers, these two
layers both contain a conductive matrix, one of the aforementioned
two layers contains at least one type of light scattering particles
that are transparent and that have a primary particle size of at
least 0.5 .mu.m and is composed of the aforementioned light
scattering particles and a component having a refractive index
equal to or higher than the refractive index of the aforementioned
organic light-emitting layer, and the other layer does not contain
light scattering particles and has a refractive index that is equal
to or higher than the refractive index of the organic
light-emitting layer.
[0145] Furthermore, the organic electroluminescent element in the
present invention is preferably such that of the two layers, the
layer that does not contain light scattering particles is adjacent
to the organic layer from the aforementioned standpoint of ensuring
flatness of the surface of the conductive layer on the side that is
in contact with the organic layer.
[0146] (Metal Electrode)
[0147] It is preferable with the organic electroluminescent element
of the present invention for either the first electrode or the
second electrode to be a conductive layer and for the remaining
other electrode, which is not a conductive layer, to be a metal
electrode. Moreover, of the aforementioned first electrode and
second electrode, the first electrode is preferably the conductive
layer, and the aforementioned metal electrode is preferably used in
the second electrode as a reflecting electrode.
[0148] Examples of the material that configures the aforementioned
metal electrode include alkali metals (such as lithium, sodium,
potassium, and cesium), alkaline earth metals (such as magnesium
and calcium), gold, silver, lead, aluminum, sodium-potassium
alloys, lithium-aluminum alloys, magnesium-silver alloys, indium,
ytterbium, and other such rare earth metals. These may be used
singly, but from the standpoint of achieving both stability and
electron injection properties, two or more types can be favorably
used together. Of these, an alkali metal or alkaline earth metal is
preferable in terms of electron injection properties, while a
material whose main component is aluminum is preferable in terms of
excellent storage stability. In addition, from the standpoint of
luminous efficiency, a material whose main component is silver,
which has high reflectivity, is preferable. The "material whose
main component is aluminum" refers to aluminum alone, an alloy of
aluminum and 0.01 to 10 wt % alkali metal or alkaline earth metal,
or a mixture of these (such as a lithium-aluminum alloy or a
magnesium-aluminum alloy). The "material whose main component is
silver" refers to silver alone, or a mixture of silver and 0.01 to
10 wt % alkaline earth metal or other metal (such as alloys of
silver with magnesium, calcium, etc.).
[0149] (Wiring with Lower Resistance than First Electrode)
[0150] It is preferable if the organic electroluminescent element
of the present invention has wiring whose resistance is lower than
that of the aforementioned first electrode (also called "auxiliary
wiring") between the first electrode and the substrate. Having
wiring whose resistance is lower than that of the first electrode
makes it possible to lower the overall resistance of the
transparent electrode combining the first electrode and the wiring,
to suppress a drop in voltage even when the emission face of the
organic electroluminescent element has a large surface area, and to
prevent uneven light emission. When the light extraction involves
diffusion, the light confined in the interior of the substrate or
the organic layer can be taken off efficiently by emitting the
light uniformly such that the emission face is large and there is
no uneven emission. The organic electroluminescent element of the
present invention more preferably has a configuration in which
there is auxiliary wiring between the first electrode and the
substrate, and the first electrode covers the auxiliary wiring. The
first electrode can be provided so as to cover the wiring
particularly by forming the first electrode by a coating method, so
the organic electroluminescent element can have a configuration in
which the wiring does not come into contact with the organic layer,
and light emission is possible over the entire surface of the
light-emitting layer.
[0151] The auxiliary wiring preferably contains a metal, more
preferably contains silver, aluminum, gold, or copper, and even
more preferably contains silver or aluminum.
[0152] The auxiliary wiring can be formed by vacuum vapor
deposition of the aforementioned metal and etching with a mask or
using photolithography. It can also be formed by printing, coating
or the like with a conductive ink that contains the aforementioned
metal.
[0153] From the standpoints of lowering the resistance of the first
electrode and suppressing the formation of bumps on the surface by
the auxiliary wiring, the thickness of the auxiliary wiring is
preferably at least 10 nm and no more than 3 .mu.m, more preferably
at least 30 nm and no more than 1 .mu.m, and even more preferably
at least 50 nm and no more than 500 nm.
[0154] From the standpoints of blocking light and lowering the
resistance of the first electrode, the width of the auxiliary
wiring is preferably at least 1 .mu.m and no more than 1 mm, more
preferably at least 5 .mu.m and no more than 500 .mu.m, and even
more preferably at least 10 .mu.m and no more than 200 .mu.m.
[0155] The shape of the auxiliary wiring can be broadly classified
by the shape of a cross section perpendicular to the layer on which
the auxiliary wiring is formed.
[0156] When auxiliary wiring in which there are angles in the shape
of the aforementioned cross section (hereinafter also referred to
as a "squared cross section") is used, the ITO layer, organic
layer, etc., laminated over the auxiliary wiring forms a layer
conforming to the shape of these angles, and there is the
possibility that electrical leakage will occur as a result of the
angular shape (steps).
[0157] On the other hand, when auxiliary wiring in which the shape
of the aforementioned cross section is rounded ((hereinafter also
referred to as a "not squared cross section") is used, the
aforementioned angular shape will not be produced, so electrical
leakage will tend not to occur.
[0158] (Other Layers)
[0159] With the organic electroluminescent element of the present
invention, preferably at least the aforementioned second electrode
and the aforementioned organic layer are sealed within a sealing
can, and more preferably the aforementioned first electrode, the
aforementioned second electrode, and the aforementioned organic
layer are sealed within a sealing can.
[0160] (Organic Layer)
[0161] The aforementioned organic layer has at least an organic
light-emitting layer. Examples of functional layers other than the
aforementioned organic light-emitting layer include a hole
transport layer, an electron transport layer, a hole blocking
layer, an electron blocking layer, a hole injection layer, and an
electron injection layer.
[0162] The aforementioned organic layer preferably has a hole
transport layer between the anode and the organic light-emitting
layer, and preferably has an electron transport layer between the
cathode and the light-emitting layer. Furthermore, a hole injection
layer may also be provided between the hole transport layer and the
anode, and an electron injection layer may also be provided between
the electron transport layer and the cathode.
[0163] Moreover, a hole transporting intermediate layer (electron
blocking layer) may also be provided between the aforementioned
organic light-emitting layer and the hole transport layer, and an
electron transporting intermediate layer (hole blocking layer) may
also be provided between the light-emitting layer and the electron
transport layer. The various functional layers may be divided into
a plurality of secondary layers.
[0164] These functional layers including the aforementioned organic
light-emitting layer can be favorably formed by a dry film
formation processes such as vapor deposition or sputtering, or by
wet coating, transfer, printing, inkjetting, or the like.
[0165] --Organic Light-Emitting Layer--
[0166] When an electric field is applied, the aforementioned
organic light-emitting layer accepts holes from the anode, the hole
injection layer, or the hole transport layer, accepts electrons
from the cathode, the electron injection layer, or the electron
transport layer, and has the function of emitting light by
providing a site for the rebinding of holes and electrons.
[0167] The aforementioned organic light-emitting layer includes a
light-emitting material. The aforementioned organic light-emitting
layer may be made up of just a light-emitting material, or it may
be a mixed layer of a host material and a light-emitting material
(in the latter case, the light-emitting material will sometimes be
called a "light-emitting dopant" or a "dopant"). The aforementioned
light-emitting material may be a fluorescent material or a
phosphorescent material, or may be a mixture of two or more types.
The host material is preferably a charge transport material. There
may be just one kind of host material, or two or more kinds may be
used. In addition, a material which does not have a charge
transporting property and does not emit light may be included in
the organic light-emitting layer.
[0168] There are no particular restrictions on the thickness of the
aforementioned organic light-emitting layer, which can be suitably
selected according to the intended use, but 2 to 500 nm is
preferable, and from the standpoint of external quantum efficiency,
3 to 200 nm is more preferable, and 5 to 100 nm is even more
preferable. Furthermore, the aforementioned organic light-emitting
layer may be a single layer or two or more layers, and the various
layers may emit light of different colors.
[0169] ----Light-emitting Material----
[0170] For the aforementioned light-emitting material, a
phosphorescent material, a fluorescent material, or the like can be
used favorably.
[0171] From the standpoint of drive durability, the aforementioned
light-emitting material is preferably a dopant such that the
difference in ionization potential (.DELTA.Ip) and the difference
in electron affinity (.DELTA.Ea) from those of the host compound
satisfy the relations 1.2 eV>.DELTA.Ip>0.2 eV and/or 1.2
eV>.DELTA.Ea>0.2 eV.
[0172] The light-emitting material in the aforementioned
light-emitting layer is generally contained in the aforementioned
light-emitting layer in an amount of 0.1 to 50 wt % with respect to
the total weight of the compound forming the light-emitting layer,
but from the standpoints of durability and external quantum
efficiency, it is preferable to be contained in an amount of 1 to
50 wt % and more preferably 2 to 50 wt %.
[0173] ----Phosphorescent Material----
[0174] A typical example of the aforementioned phosphorescent
material is complexes containing transition metal atoms or
lanthanoid atoms.
[0175] There are no particular restrictions on the aforementioned
transition metal atoms, which can be suitably selected according to
the intended use, [but] examples include ruthenium, rhodium,
palladium, tungsten, rhenium, osmium, iridium, gold, silver,
copper, and platinum. [Of these,] rhenium, iridium, and platinum
are more preferable, and iridium and platinum are even more
preferable.
[0176] Examples of ligands of the aforementioned complex include
those discussed in "Comprehensive Coordination Chemistry," by G.
Wilkinson et al., Pergamon Press (1987), "Photochemistry and
Photophysics of Coordination Compounds," by H. Yersin,
Springer-Verlag (1987), and "Yuuki Kinzoku Kagaku--Kiso to Ouyou
[Organometallic Chemistry--Fundamentals and Applications]," by A.
Yamamoto, Shokabo (1982).
[0177] The aforementioned complex may have just one transition
metal atom in the compound, or may be a so-called dinuclear complex
having two or more transition metal atoms. Different kinds of metal
atoms may also be contained at the same time.
[0178] Of these, examples of phosphorescent materials include the
phosphorescent compounds or the like described in publications of
U.S. Pat. No. 6,303,238 B1, U.S. Pat. No. 6,097,147, WO 00/57676,
WO 00/70655, WO 01/08230, WO 01/39234 A2, WO 01/41512 A1, WO
02/02714 A2, WO 02/15645 A1, WO 02/44189 A1, WO 05/19373 A2, WO
2004/108857 A1, WO 2005/042444 A2, WO 2005/042550 A1, Japanese
Laid-Open Patent Applications 2001-247859, 2002-302671,
2002-117978, 2003-133074, 2002-235076, 2003-123982, and
2002-170684, EP 1211257, and Japanese Laid-Open Patent Applications
2002-226495, 2002-234894, 2001-247859, 2001-298470, 2002-173674,
2002-203678, 2002-203679, 2004-357791, 2006-93542, 2006-261623,
2006-256999, 2007-19462, 2007-84635, and 2007-96259. Of these,
iridium complexes, platinum complexes, copper complexes, rhenium
complexes, tungsten complexes, rhodium complexes, ruthenium
complexes, palladium complexes, osmium complexes, europium
complexes, terbium complexes, gadolinium complexes, dysprosium
complexes, and cerium complexes are preferred, with iridium
complexes, platinum complexes, and rhenium complexes being more
preferred. Iridium complexes, platinum complexes, and rhenium
complexes including at least one coordination mode from among
metal-carbon bonds, metal-nitrogen bonds, metal-oxygen bonds, and
metal-sulfur bonds are even more preferred. From the standpoints of
luminous efficiency, drive durability, chromaticity, and so forth,
iridium complexes, platinum complexes, and rhenium complexes
including tridentate or higher polydentate ligand are particularly
preferred.
[0179] The following compounds can be listed as concrete examples
of the aforementioned phosphorescent material, but [the
phosphorescent material] is not limited to these:
[First Chemical Formula]
##STR00001## ##STR00002## ##STR00003## ##STR00004##
[0180] [Second Chemical Formula]
##STR00005## ##STR00006## ##STR00007## ##STR00008##
[0181] [Third Chemical Formula]
##STR00009##
[0183] ------Fluorescent Material------
[0184] There are no particular restrictions on the aforementioned
fluorescent material, which can be suitably selected according to
the intended use, [but] examples include benzoxazole,
benzoimidazole, benzothiazole, styrylbenzene, polyphenyl,
diphenylbutadiene, tetraphenylbutadiene, naphthalimide, coumarin,
pyran, perinone, oxadiazole, aldazine, pyridine, cyclopentadiene,
bis-styrylanthracene, quinacridone, pyrrolopyridine,
thiadiazolopyridine, cyclopentadiene, styrylamine, aromatic
dimethylidene compounds, condensed polyaromatic compounds (such as
anthracene, phenanthroline, pyrene, perylene, rubrene, and
pentacene), various types of metal complex (typified by metal
complexes of 8-quinolynol, pyromethene complexes, and rare earth
complexes), polymer compounds (such as polythiophene,
polyphenylene, and polyphenylenevinylene), organosilanes, and
derivatives of these.
[0185] ----Host Material----
[0186] For the aforementioned host material, a hole transporting
host material with excellent hole transporting properties (may also
be referred to as a "hole transporting host") or an electron
transporting host compound with excellent electron transporting
properties (may also be referred to as an "electron transporting
host") can be used.
[0187] ------Hole Transporting Host Material------
[0188] The following materials can be listed as examples of the
aforementioned hole transporting host material: namely, pyrrole,
indole, carbazole, azaindole, azacarbazole, triazole, oxazole,
oxadiazole, pyrazole, imidazole, thiophene, polyarylalkane,
pyrazoline, pyrazolone, phenylenediamine, arylamine,
amino-substituted chalcone, styrylanthracene, fluorenone,
hydrazone, stilbene, silazane, aromatic tertiary amine compounds,
styrylamine compounds, aromatic dimethylidine compounds, porphyrin
compounds, polysilane compounds, poly(N-vinylcarbazole), aniline
copolymers, conductive high-molecular-weight oligomers (such as
thiophene oligomers and polythiophenes), organosilanes, carbon
films, and derivatives of these.
[0189] Of these, indole derivatives, carbazole derivatives,
aromatic tertiary amine compounds, thiophene derivatives, and
compounds containing a carbazole group in the molecule are
preferable, and compounds containing a t-butyl-substituted
carbazole group are more preferable.
[0190] ------Electron Transporting Host Material------
[0191] Examples of the electron transporting host material include
pyridine, pyrimidine, triazine, imidazole, pyrazole, triazole,
oxazole, oxadiazole, fluorenone, anthraquinonedimethane, anthrone,
diphenylquinone, thiopyrane dioxide, carbodiimide,
fluorenylidenemethane, distyrylpyradine, fluorine-substituted
aromatic compounds, heterocyclic tetracarboxylic acid anhydrides
(such as naphthalene [and] perylene), phthalocyanine, derivatives
of these (which may form a condensed ring with another ring), and
various metal complexes typified by a metal complex of an
8-quinolinol derivative, a metal phthalocyanine, and a metal
complex containing benzoxazole or benzothiazole as a ligand. Of
these, metal complex compounds are preferable from the standpoint
of durability, and metal complexes having a ligand with at least
one nitrogen atom, oxygen atom, or sulfur atom coordinated with the
metal are more preferable. Examples of the aforementioned metal
complex electron transporting host include the compounds described
in publications of Japanese Laid-Open Patent Applications
2002-235076, 2004-214179, 2004-221062, 2004-221065, 2004-221068,
and 2004-327313.
[0192] The following compounds can be listed as concrete examples
of the aforementioned hole transporting host material and electron
transporting host material, but [the compounds] are not limited to
these:
[Fourth Chemical Formula]
##STR00010## ##STR00011##
[0193] [Fifth Chemical Formula]
##STR00012## ##STR00013## ##STR00014## ##STR00015##
[0194] [Sixth Chemical Formula]
##STR00016##
[0196] --Hole Injection Layer and Hole Transport Layer--
[0197] The aforementioned hole injection layer or the
aforementioned hole transport layer is a layer having the function
of accepting holes from the anode or from a layer on the anode side
and transporting them to the cathode side. The hole injection
material and hole transport material used in these layers may be a
low-molecular-weight compound or a high-molecular-weight compound.
In concrete terms, the layers preferably contain a pyrrole
derivative, a carbazole derivative, a triazole derivative, an
oxazole derivative, an oxadiazole derivative, an imidazole
derivative, a polyarylalkane derivative, a pyrazoline derivative, a
pyrazolone derivative, a phenylenediamine derivative, an arylamine
derivative, an amino-substituted chalcone derivative, a
styrylanthracene derivative, a fluorenone derivative, a hydrazone
derivative, a stilbene derivative, a silazane derivative, an
aromatic tertiary amine compound, a styrylamine compound, an
aromatic dimethylidine compound, a phthalocyanine compound, a
porphyrin compound, a thiophene derivative, an organosilane
derivative, carbon, or the like.
[0198] An electron accepting dopant can be contained in the
aforementioned hole injection layer or the aforementioned hole
transport layer. Either an inorganic compound or organic compound
can be used as the electron accepting dopant introduced into the
aforementioned hole injection layer or the hole transport layer as
long as it has an electron accepting property and serves to oxidize
an organic compound.
[0199] In concrete terms, examples of inorganic compounds include
metal halides (such as ferric chloride, aluminum chloride, gallium
chloride, indium chloride, and antimony pentachloride) and metal
oxides (such as vanadium pentoxide and molybdenum trioxide). In the
case of an organic compound, it is preferable to use a compound
having as a substituent a nitro group, a halogen, a cyano group, a
trifluoromethyl group, or the like, a quinone compounds, an acid
anhydride compounds, fullerene, or the like.
[0200] These electron accepting dopants may be used singly, or two
or more types may be used. The amount in which the electron
accepting dopant is used will vary with the type of material, but
it is preferably 0.01 to 50 wt %, more preferably 0.05 to 40 wt %,
and particularly preferably 0.1 to 30 wt %, with respect to the
hole transport layer material.
[0201] The aforementioned hole injection layer or hole transport
layer may have a single-layer structure composed of one or more
types of the aforementioned materials, or may have a multilayer
structure composed of a plurality of layers of the same composition
or different compositions.
[0202] --Electron Injection Layer and Electron Transport
Layer--
[0203] The aforementioned electron injection layer or the
aforementioned electron transport layer is a layer having the
function of accepting electrons from the cathode or a layer on the
cathode side and transporting them to the anode side. The electron
injection material and electron transport material used in these
layers may be a low-molecular-weight compound or a
high-molecular-weight compound.
[0204] In concrete terms, it is preferable to use a layer
containing a pyridine derivative, a quinoline derivative, a
pyrimidine derivative, a pyrazine derivative, a phthalazine
derivative, a phenanthoroline derivative, a triazine derivative, a
triazole derivative, an oxazole derivative, an oxadiazole
derivative, an imidazole derivative, a fluorenone derivative, an
anthraquinodimethane derivative, an anthrone derivative, a
diphenylquinone derivative, a thiopyrane dioxide derivative, a
carbodiimide derivative, a fluorenylidenemethane derivative, a
distyrylpyradine derivative, an aromatic tetracarboxylic acid
anhydride such as perylene or naphthalene, a phthalocyanine
derivative, various metal complexes typified by a metal complex of
an 8-quinolinol derivative, a metal phthalocyanine, and a metal
complex containing benzoxazole or benzothiazole as a ligand, an
organosilane derivative typified by silole, or the like.
[0205] An electron donating dopant can be contained in the
aforementioned electron injection layer or electron transport
layer. The electron donating dopant introduced into the
aforementioned electron injection layer or electron transport layer
may be any material having an electron donating property and a
property for reducing organic compounds, and alkali metals such as
lithium, alkaline earth metals such as magnesium, transition metals
including rare earth metals, reductive organic compounds, and the
like are favorably used. Metals that can be used particularly
favorably are those having a work function of 4.2 eV or less,
concrete examples of which include lithium, sodium, potassium,
beryllium, magnesium, calcium, strontium, barium, yttrium, cesium,
lanthanum, samarium, gadolinium, and ytterbium. Furthermore,
examples of reductive organic compounds include nitrogen-containing
compounds, sulfur-containing compounds, and phosphorus-containing
compounds.
[0206] These electron donating dopants may be used singly, or two
or more types may be used. The amount in which the electron
donating dopant is used will vary with the type of material, but it
is preferably 0.1 to 99 wt %, more preferably 1.0 to 80 wt %, and
particularly preferably 2.0 to 70 wt %, with respect to the
electron transport layer material.
[0207] The aforementioned electron injection layer or the
aforementioned electron transport layer may have a single-layer
structure composed of one or more types of the aforementioned
materials, or may have a multilayer structure composed of a
plurality of layers of the same composition or different
compositions.
[0208] --Hole Blocking Layer and Electron Blocking Layer--
[0209] The aforementioned hole blocking layer is a layer having the
function of preventing the holes transported from the anode side to
the organic light-emitting layer from escaping to the cathode side,
and is usually provided as an organic compound layer that is
adjacent to the light-emitting layer on the cathode side.
[0210] Meanwhile, the aforementioned electron blocking layer is a
layer having the function of preventing the electrons transported
from the cathode side to the organic light-emitting layer from
escaping to the anode side, and is usually provided as an organic
compound layer that is adjacent to the organic light-emitting layer
on the anode side.
[0211] Examples of compounds that constitute the aforementioned
hole blocking layer include BAlq and other such aluminum complexes,
triazole derivatives, and phenanthroline derivatives such as BCP.
Compounds given for the hole transport material above can be
utilized as examples of compounds that constitute the electron
blocking layer.
[0212] The thickness of the aforementioned hole blocking layer and
electron blocking layer is preferably 1 to 500 nm, more preferably
5 to 200 nm, and even more preferably 10 to 100 nm. Moreover, the
aforementioned hole blocking layer and electron blocking layer may
have a single-layer structure composed of one or more types of the
aforementioned materials, or may have a multilayer structure
composed of a plurality of layers of the same composition or
different compositions.
[0213] --Sealing Can--
[0214] There are no particular restrictions on the aforementioned
sealing can so long as it has a size, shape, structure, and so
forth that allow the sealing of an organic electroluminescent
element including a first electrode, a second electrode, and an
organic layer, and it can be suitably selected according to the
intended use.
[0215] A moisture absorbent or an inert liquid may be sealed in the
space between the aforementioned sealing can and the organic
electroluminescent element including the first electrode, second
electrode, and organic layer.
[0216] There are no particular restrictions on the aforementioned
moisture absorbent, which can be suitably selected according to the
intended use, [but] examples include barium oxide, sodium oxide,
potassium oxide, calcium oxide, sodium sulfate, calcium sulfate,
magnesium sulfate, phosphorus pentoxide, calcium chloride,
magnesium chloride, copper chloride, cesium fluoride, niobium
fluoride, calcium bromide, vanadium bromide, molecular sieves,
zeolites, and magnesium oxide.
[0217] There are no particular restrictions on the aforementioned
inert liquid, which can be suitably selected according to the
intended use, [but] examples include paraffins, liquid paraffins,
fluorine-based solvents such as perfluoroalkane, perfluoroamine,
and perfluoroether, chlorine-based solvents, and silicone oils.
[0218] The aforementioned organic electroluminescent element can be
configured as a device capable of display in full color.
[0219] Known methods for making the aforementioned organic
electroluminescent element a full-color type include, for example,
as discussed in Gekkan Disuprei [Monthly Display], September, 2000,
pp. 33-37, a three-color light-emitting method in which a layer
structure that emits light corresponding to each of the three
primary colors (blue (B), green (G), and red (R)) is disposed on a
substrate, a white method in which white light emitted from a layer
structure for white light emission is passed through a color filter
layer and separated into the three primary colors, and a color
conversion method in which blue light emitted from a layer
structure for blue light emission is passed through a fluorescent
dye layer and converted into red (R) and green (G).
[0220] In this case, the laser power and thickness are preferably
adjusted as appropriate for each blue (B), green (G), and red (R)
pixel.
[0221] In addition, a plurality of layer structures of different
emission colors obtained by the aforementioned methods may be used
in combination to obtain a flat light source of the desired
emission colors. For instance, [this can be] a white emission light
source that combines blue and yellow light-emitting devices, a
white emission light source that combines blue (B), green (G), and
red (R) organic electroluminescent elements, or the like.
[0222] The aforementioned organic electroluminescent element can be
used favorably in a variety of fields such as lighting devices,
computers, onboard displays, outdoor displays, household devices,
commercial devices, consumer devices, traffic displays, clock and
watch displays, calendar displays, luminescent screens, and
acoustic devices.
Working Examples
[0223] Working examples of the present invention will be described
below, but the present invention is in no way limited to or by
these working examples.
[0224] <Average Thickness of Conductive Layer, Diffused Layer,
and Planarization Layer>
[0225] The average thickness of the conductive layer, the diffused
layer, and the planarization layer can be found by cutting out part
of each layer and measuring it with a scanning electron microscope
(S-3400N, made by Hitachi High-Technologies Corporation).
[0226] <Measurement of Refractive Index>
[0227] The refractive index of the conductive layer was found by
forming, on a silicon substrate or a quartz substrate, a film of a
component having a refractive index equal to or higher than the
refractive index of the aforementioned organic light-emitting layer
in a thickness approximately corresponding to the wavelength of the
light and measuring the refractive index of the film thus formed on
the substrate with an ellipsometer.
[0228] The refractive index of the planarization layer and the
refractive index of the conductive polymer of the conductive layer
can be found in the same way.
[0229] <Production of Organic Electroluminescent Element>
[0230] --Production of Diffused Conductive Layer Coating Solution
1--
[0231] PEDOT-PSS
(poly(3,4-ethylenedioxythiophene)-poly(styrenesulfonic acid)) was
doped with a slurry in which titanium oxide (TiO.sub.2) particles
(with a primary particle size of 100 nm or less) were dispersed,
and [this product] was thoroughly stirred with an omnimixer to
obtain a conductive binder material. The refractive index of the
aforementioned PEDOT-PSS was 1.50.
[0232] Note that the aforementioned titanium oxide particles used
in the following working examples and comparative examples have all
been given a surface treatment with aluminum oxide or the like for
suppressing the photoactivity of the titanium oxide, and the
refractive index thereof was 2.40.
[0233] The volumetric ratio of PEDOT-PSS and titanium oxide
particles should be one at which the necessary refractive index
will be obtained, and with pure titanium oxide, [the ratio] is
about PEDOT-PSS:titanium oxide=7:3 to 6:4, but with a mixture or
particles having a shell-core structure, the ratio should be
adjusted as appropriate so as to obtain the necessary refractive
index.
[0234] Transparent particles with a high refractive index (such as
zirconium oxide particles or another such particulate transparent
material) or particles in the form of a slurry or sol may be added
instead of titanium oxide.
[0235] Next, light scattering particles having the desired size
(such as "MX-150," made by Soken Chemical & Engineering, which
is crosslinked acrylic particles with a primary particle size of
1.5 .mu.m) were stirred with a stirrer while being used to dope the
aforementioned conductive binder material. The light scattering
particles were then thoroughly dispersed with an omnimixer, which
gave a diffused conductive layer coating solution 1.
[0236] An inorganic material (such as zirconium oxide or titanium
oxide) with a size of about 1 to 10 .mu.m may be added instead of
the crosslinked acrylic or other resin particles.
[0237] The refractive index of the conductive binder was 1.8
(PEDOT-PSS+titanium oxide slurry), and the refractive index of the
light scattering particles was 1.49 (in the case of the crosslinked
acrylic particles), so there was a sufficiently large difference in
the refractive index, and diffusion that was adequate for light
extraction was obtained even with a thin film.
[0238] The volumetric ratio of the light scattering particles and
the conductive binder material was about 50:50 with conductive
binder:light scattering particles MX-150, but when flatness is
taken into account, [the ratio] may be lowered to about 70:30 to
80:20.
[0239] --Production of Diffused Conductive Layer Coating Solution
2--
[0240] Just as in the "production of diffused conductive layer
coating solution 1" described above, a slurry in which titanium
oxide particles were dispersed was used to dope PEDOT-PSS, and
[this product] was thoroughly stirred with an omnimixer, which gave
a diffused conductive layer coating solution 2.
[0241] The volumetric ratio of the PEDOT-PSS and the titanium oxide
particles should be one at which the necessary refractive index
will be obtained, and with titanium oxide, [the ratio] is about 7:3
to 6:4.
[0242] Transparent particles with a high refractive index (such as
zirconium oxide particles or another such particulate transparent
material) may be added instead of titanium oxide.
Production of Coating Material for Planarization Layer
Comparative Example
[0243] A titanium oxide dispersion (a dispersion of nanoparticles
of titanium oxide with a primary particle size of 15 nm; material
name: titanium oxide-dispersed toluene, trade name: HTD-760T High
Transparency Titanium Oxide Slurry), a resin material (material
name: fluorene derivative, trade name: OGSOL EA-0200 (hereinafter
also referred to as "binder")), and toluene were dissolved and
stirred with a roller and stirrer, and then the nanoparticles were
thoroughly dispersed in the binder by ultrasonic waves to obtain a
coating material for the planarization layer.
Production of Coating Material for Diffused Layer
Comparative Example
[0244] Light scattering particles (crosslinked acrylic particles
with a primary particle size of 1.5 .mu.m, material name: EX-150)
and a toluene solvent were stirred with a stirrer while being used
to dope the aforementioned coating material for the planarization
layer.
[0245] The light scattering particles were then thoroughly
dispersed in a base material by ultrasonic waves and further
stirred well with a stirrer or the like to obtain a coating
material for the diffused layer.
[0246] The refractive index of the base material (titanium oxide
and binder dispersion) during curing was 1.8, and the refractive
index of the light scattering particles was 1.49, so the difference
in the refractive index was sufficiently large, and diffusion that
was adequate for light extraction was obtained even with a thin
film.
[0247] In addition, since toluene was used as the solvent, the
resin particles need to have adequate solvent resistance, but here
again, this combination of materials stands up well to solvents,
and was extremely superior in regard to degradation of the
dispersion (clumping, etc.) due to changes over time.
[0248] --Glass Substrate Surface Treatment--
[0249] The glass substrate was subjected to a silane coupling
treatment to improve adhesion between the diffused layer and the
glass. In cases where a diffused conductive layer coating solution
is used, this treatment is unnecessary, and an ordinary glass
substrate treatment (washing) that is performed prior to the
formation of a film of an organic layer or ITO may be carried
out.
[0250] --Film Formation of Photolithographic Auxiliary Wiring--
[0251] After the film formation of the diffused layer or
planarization layer, a 100-nm film of silver was formed as
auxiliary wiring by vacuum vapor deposition, and this was put into
the auxiliary wiring shape by photolithography.
[0252] --Film Formation of Mask Auxiliary Wiring--
[0253] After the film formation of the diffused layer or
planarization layer, a 100-nm film of silver was formed with a
metal mask as auxiliary wiring by vacuum vapor deposition. The
resulting shape by a metal mask became more rounded than the wiring
shape obtained by etching.
[0254] --Film Formation of Diffused Conductive Layer 1--
[0255] The aforementioned diffused conductive layer coating
solution 1 was used to coat the aforementioned substrate with an
edge coater. After this coating, [the film] was dried and cured in
a 120.degree. C. environment, which gave a diffused conductive
layer (first electrode).
[0256] --Film Formation of Diffused Conductive Layer 2--
[0257] Depending on the degree of unevenness on the surface of the
diffused conductive layer 1, a diffused conductive layer coating
solution 2 may be applied over the diffused conductive layer 1.
[0258] This can be used not only to ensure flatness, but also to
adjust the diffusion effect. The refractive index of the two layers
may also be varied.
Production of Planarization Layer and Diffused Layer
Comparative Example
[0259] A polymerization initiator was added to the completed
coating material of the planarization layer and the coating
material of the diffused layer.
[0260] A glass substrate that had been washed and given a surface
treatment was coated with the coating material of the diffused
layer using a wire bar, after which [the coating] was cured for 10
minutes under UV irradiation (365 nm), which gave a diffused layer
(5 .mu.m).
[0261] The diffused layer was coated with the coating material of
the planarization layer using a wire bar, and [the coating] was
cured under UV irradiation, which gave a laminated diffused layer
and planarization layer.
Film Formation of ITO (First Electrode)
Comparative Example
[0262] ITO was formed in [a thickness of] 100 nm using a sputtering
device over the planarization (diffused) layer formed on the
substrate.
[0263] --Production of Organic Electroluminescent Light-emitting
Layer (Organic EL Layer)--
[0264] A vacuum vapor deposition apparatus was used to deposit
HAT-CN (10 nm), 2-TNATA
(4,4',4''-tris(N,N-(2-naphthyl)-phenylamino)triphenylamine: 99.9
vol %), and F4-TCNQ (0.2 vol %) (co-deposited at 160 nm) on the
first electrode on the substrate produced by the aforementioned
method, thus forming a hole injection layer.
[0265] NPD (bis[N-(1-naphthyl)-N-phenyl]benzidine) (10 nm), mCP
(1,3-bis(carbazol-9-yl)benzene: 60 vol %), and a light-emitting
material A (40 vol %) (co-deposited at 30 nm) were deposited over
this to form an organic light-emitting layer.
[0266] Furthermore, BAlq
(bis-(2-methyl-8-quinolinolato)-4-(phenyl-phenolate)-aluminum(III))
was laminated [over this] (40 nm) to form an electron transport
layer, which gave an organic layer.
[0267] Note that the organic light-emitting layer in the organic
layer thus obtained had a refractive index of 1.70.
[Seventh Chemical Formula]
##STR00017##
[0268] [Eighth Chemical Formula]
##STR00018##
[0269] [Ninth Chemical Formula]
##STR00019##
[0270] [Tenth Chemical Formula]
##STR00020##
[0271] [Eleventh Chemical Formula]
##STR00021##
[0272] [Twelfth Chemical Formula]
##STR00022##
[0273] [Thirteenth Chemical Formula]
##STR00023##
[0275] --Production of Reflecting Electrode (Second
Electrode)--
[0276] LiF (1 nm) and, as electrodes, aluminum (either 100 nm or
0.5 nm) and silver (100 nm) were applied by vapor deposition.
[0277] --Sealing--
[0278] The organic layer side of the substrate was sealed with a
sealing glass can in which a desiccant was affixed in a nitrogen
gas atmosphere, and the side where the substrate was installed was
coated with a sealing material.
Working Example 1
[0279] The diffused conductive layer coating solution 1 was
obtained by the aforementioned method using a conductive polymer
(PEDOT-PSS), refractive index control particles (TiO.sub.2), and
light scattering particles (PMMA; primary particle size of 1.5
.mu.m) in a volumetric ratio of 30:20:30.
[0280] The organic electroluminescent element of Working Example 1
was obtained by performing a glass substrate surface treatment,
film formation of the diffused conductive layer 1 (first
electrode), production of the organic EL layer, and production of
the reflecting electrode (second electrode), and performing the
aforementioned sealing.
[0281] FIG. 1 is a schematic diagram showing the configuration of
the organic electroluminescent elements in Working Example 1 as
well as Working Examples 4 and 9 to 11 and Comparative Examples 2,
6, and 7 described below.
[0282] The size of the emission face of the organic
electroluminescent element was 10.times.10 mm.
Working Example 2
[0283] Other than installing auxiliary wiring on a glass substrate
by photolithographic auxiliary wiring film formation and setting
the size of the emission face of the organic electroluminescent
element to 30.times.30 mm, the same operation as in Working Example
1 was performed to obtain the organic electroluminescent element of
Working Example 2. A schematic diagram showing the configuration of
the organic electroluminescent element in Working Example 2 is
shown in FIG. 2.
Working Example 3
[0284] Other than installing auxiliary wiring on a glass substrate
by mask auxiliary wiring film formation and setting the size of the
emission face of the organic electroluminescent element to
30.times.30 mm, the same operation as in Working Example 1 was
performed to obtain the organic electroluminescent element of
Working Example 3. A schematic diagram showing the configuration of
the organic electroluminescent element in Working Example 3 is
shown in FIG. 3.
Working Example 4
[0285] Other than changing the light scattering particles with a
primary particle size of 1.5 .mu.m to light scattering particles
with a primary particle size of 12 .mu.m and changing the thickness
of the coating-type diffused conductive layer to 12 .mu.m, the same
operation as in Working Example 1 was performed to obtain the
organic electroluminescent element of Working Example 4.
Working Example 5
[0286] The diffused conductive layer coating solution 2 was
produced using the material given in Table 1. Other than making the
diffused conductive layer to a two-layer configuration of the
diffused conductive layer 1 and the diffused conductive layer 2 and
changing the reflecting electrode to aluminum/silver, the same
operation as in Working Example 3 was performed to obtain the
organic electroluminescent element of Working Example 5. FIG. 4 is
a schematic diagram showing the configuration of the organic
electroluminescent elements in Working Example 5 as well as Working
Examples 6 to 8 described below.
Working Examples 6 to 8
[0287] Other than using the materials given in Table 1 to produce
the diffused conductive layer coating solutions 1 and 2, the same
operation as in Working Example 5 was performed to obtain the
organic electroluminescent elements of Working Examples 6 to 8.
Working Example 9
[0288] Other than changing the light scattering particles used for
the diffused conductive layer coating solution 1 from PMMA
particles (with a primary particle size of 1.5 .mu.m) to
silica-melamine resin particles (with a primary particle size of
2.0 .mu.m), the same operation as in Working Example 1 was
performed to obtain the organic electroluminescent element of
Working Example 9.
Working Example 10
[0289] Other than changing the refractive index control particles
used for the diffused conductive layer coating solution 1 from
titanium oxide (n=2.4) to zirconium oxide (n=2.4), the same
operation as in Working Example 1 was performed to obtain the
organic electroluminescent element of Working Example 10.
Working Example 11
[0290] Other than changing the refractive index control particles
used for the diffused conductive layer coating solution 1 from
titanium oxide (n=2.4) to zinc oxide (n=1.95) and readjusting the
blend ratio, the same operation as in Working Example 1 was
performed to obtain the organic electroluminescent element of
Working Example 11.
Comparative Example 1
[0291] A coating material for the planarization layer and a coating
material for the diffused layer were produced using the materials
given in Table 2. Then, the organic electroluminescent element of
Comparative Example 1 was obtained by performing a glass substrate
surface treatment, production of the planarization layer and
diffused layer, film formation of ITO (first electrode), production
of the organic EL layer, and production of the reflecting electrode
(second electrode), and performing sealing. FIG. 5 is a schematic
diagram showing the configuration of the organic electroluminescent
element of Comparative Example 1. The size of the emission face of
the organic electroluminescent element was 10.times.10 mm.
Comparative Example 2
[0292] Other than changing the light scattering particles with a
primary particle size of 1.5 .mu.m to light scattering particles
with a primary particle size of 0.3 .mu.m, the same operation as in
Working Example 1 was performed to obtain the organic
electroluminescent element of Comparative Example 2.
Comparative Example 3
[0293] Other than installing auxiliary wiring on ITO by
photolithographic auxiliary wiring film formation and setting the
size of the emission face of the organic electroluminescent element
to 30.times.30 mm, the same operation as in Comparative Example 1
was performed to obtain the organic electroluminescent element of
Comparative Example 3. A schematic diagram showing the
configuration of the organic electroluminescent element in
Comparative Example 3 is shown in FIG. 6.
Comparative Example 4
[0294] Other than using a coating-type diffused conductive layer
that did not contain refractive index control particles, the same
operation as in Working Example 2 was performed to obtain the
organic electroluminescent element of Comparative Example 4. FIG. 7
is a schematic diagram showing the configuration of the organic
electroluminescent element in Comparative Example 4.
Comparative Example 5
[0295] Other than forming auxiliary wiring on ITO by mask auxiliary
wiring film formation, then coating the auxiliary wiring with a
protective resist, and increasing the thickness of the hole
injection layer, the same operation as in Comparative Example 3 was
performed to obtain the organic electroluminescent element of
Comparative Example 5. FIG. 8 is a schematic diagram showing the
configuration of the organic electroluminescent element in
Comparative Example 5.
Comparative Example 6
[0296] Other than using a conductive layer formed by removing the
light scattering particles from the diffused conductive layer
coating solution 1, the same operation as in Working Example 1 was
performed to obtain the organic electroluminescent element of
Comparative Example 6.
Comparative Example 7
[0297] Other than changing the refractive index control particles
used for the diffused conductive layer coating solution 1 from
titanium oxide (n=2.4) to aluminum oxide (alumina, n=1.8), the same
operation as in Working Example 1 was performed to obtain the
organic electroluminescent element of Comparative Example 7.
Comparative Example 0
[0298] Other than forming a film of ITO directly on a glass
substrate, the same operation as in Comparative Example 1 was
performed to obtain the organic electroluminescent element of
Comparative Example 0. FIG. 9 is a schematic diagram showing the
configuration of the organic electroluminescent element in
Comparative Example 0. The organic electroluminescent elements in
two types were produced with the sizes of the emission face being
10.times.10 mm and 30.times.30 mm.
[0299] As discussed below, the light extraction efficiency of other
organic electroluminescent devices was evaluated by using
Comparative Example 0 as a standard (reference element).
[0300] The light extraction efficiency of the organic
electroluminescent devices thus produced was evaluated as
follows:
[0301] <Measurement of Light Extraction Efficiency>
[0302] Each of the organic electroluminescent elements was made to
emit light by applying a constant DC current of 2.5 mA/cm.sup.2,
and the radiation strength was measured using a CS2000
spectrophotometer made by Konica Minolta, Inc. Then, the light
extraction efficiency of the aforementioned organic
electroluminescent element was calculated from the following
formula:
light extraction efficiency (times)=(radiation strength of organic
electroluminescent element/radiation strength of reference
element)
[0303] The results are given in Tables 1 and 2 below.
TABLE-US-00001 TABLE 1 Working Ex. 1 Working Ex. 2 Working Ex. 3
Working Ex. 4 Organic EL yes yes yes yes layer (Al electrode) (Al
electrode) (Al electrode) (Al electrode) Conductive coating-type
diffused coating-type diffused coating-type diffused coating-type
diffused layer conductive layer conductive layer conductive layer
conductive layer (PEDOT-PSS)/ (PEDOT-PSS)/ (PEDOT-PSS)/
(PEDOT-PSS)/ refractive index control refractive index control
refractive index control refractive index control particles
(TiO.sub.2)/light particles (TiO.sub.2)/light particles
(TiO.sub.2)/light particles (TiO.sub.2)/light scattering particles
scattering particles scattering particles scattering particles
(PMMA, primary (PMMA, primary (PMMA, primary (PMMA, primary
particle size 1.5 .mu.m) = particle size 1.5 .mu.m) = particle size
1.5 .mu.m) = particle size 12 .mu.m) = 30/20/30 30/20/30 30/20/30
30/20/30 thickness: 5 .mu.m thickness: 5 .mu.m thickness: 5 .mu.m
thickness: 12 .mu.m refractive index: 1.80 refractive index: 1.80
refractive index: 1.80 refractive index: 1.80 Auxiliary no yes yes
no wiring Ag (100 nm) Ag (100 nm) formed by photo- formed by vapor
lithography (squared deposition (not squared cross section) cross
section) Light 175% 177% 179% 165% extraction efficiency Working
Ex. 5 Working Ex. 6 Working Ex. 7 Working Ex. 8 Organic EL yes yes
yes yes layer (Al/Ag electrode) (Al/Ag electrode) (Al/Ag electrode)
(Al/Ag electrode) Conductive coating-type diffused coating-type
diffused coating-type diffused coating-type diffused layer
conductive layer (two- conductive layer (two- conductive layer
(two- conductive layer (two- layer configuration) layer
configuration) layer configuration) layer configuration) First
layer (substrate First layer (substrate First layer (substrate
First layer (substrate side) side) side) side) coating-type
diffused coating-type diffused coating-type diffused coating-type
diffused conductive layer conductive layer conductive layer
conductive layer (PEDOT-PSS)/ (PEDOT-PSS)/ (PEDOT-PSS)/
(PEDOT-PSS)/ refractive index control refractive index control
refractive index control refractive index control particles
(TiO.sub.2)/light particles (TiO.sub.2)/light particles
(TiO.sub.2)/light particles (TiO.sub.2)/light scattering particles
scattering particles scattering particles scattering particles
(PMMA, primary (PMMA, primary (PMMA, primary (PMMA, primary
particle size 1.5 .mu.m) = particle size 1.5 .mu.m) = particle size
1.5 .mu.m) = particle size 1.5 .mu.m) = 30/20/30 25/25/50 35/15/50
40/10/50 thickness: 5 .mu.m thickness: 5 .mu.m thickness: 5 .mu.m
thickness: 5 .mu.m refractive index: 1.80 refractive index: 1.85
refractive index: 1.75 refractive index: 1.70 Second layer (organic
Second layer (organic Second layer (organic Second layer (organic
layer side) layer side) layer side) layer side) coating-type
diffused coating-type diffused coating-type diffused coating-type
diffused conductive layer conductive layer conductive layer
conductive layer (PEDOT-PSS)/ (PEDOT-PSS)/ (PEDOT-PSS)/
(PEDOT-PSS)/ refractive index control refractive index control
refractive index control refractive index control particles
(TiO.sub.2) = particles (TiO.sub.2) = particles (TiO.sub.2) =
particles (TiO.sub.2) = 60/40 50/50 70/30 80/20 thickness: 2 .mu.m
thickness: 2 .mu.m thickness: 2 .mu.m thickness: 2 .mu.m refractive
index: 1.80 refractive index: 1.85 refractive index: 1.75
refractive index: 1.70 Auxiliary yes yes yes yes wiring Ag (100 nm)
Ag (100 nm) Ag (100 nm) Ag (100 nm) formed by vapor formed by vapor
formed by vapor formed by vapor deposition (not squared deposition
(not squared deposition (not squared deposition (not squared cross
section) cross section) cross section) cross section) Light 205%
198% 193% 185% extraction efficiency Working Ex. 9 Working Ex. 10
Working Ex. 11 Organic EL yes yes yes layer (Al electrode) (Al
electrode) (Al electrode) Conductive coating-type diffused
coating-type diffused coating-type diffused layer conductive layer
conductive layer conductive layer (PEDOT-PSS)/ (PEDOT-PSS)/
(PEDOT-PSS)/ refractive index control refractive index control
refractive index control particles (TiO.sub.2)/light particles
(ZrO)/light particles (ZnO)/light scattering particles scattering
particles scattering particles (silica-melamine resin, (PMMA,
primary (PMMA, primary primary particle size particle size 1.5
.mu.m) = particle size 1.5 .mu.m) = 2.0 .mu.m) = 30/20/30 30/20/30
15/35/30 thickness: 5 .mu.m thickness: 5 .mu.m thickness: 5 .mu.m
refractive index: 1.80 refractive index: 1.80 refractive index:
1.80 Auxiliary no no no wiring Light 172% 175% 168% extraction
efficiency
TABLE-US-00002 TABLE 2 Comparative Ex. 1 Comparative Ex. 2
Comparative Ex. 3 Comparative Ex. 4 Conductive ITO (100 nm)
coating-type diffused ITO (100 nm) coating-type diffused layer
(refractive index: conductive layer (refractive index: conductive
layer 2.0) (PEDOT-PSS)/ 2.0) (PEDOT-PSS)/light refractive index
control scattering particles particles (TiO.sub.2)/light (PMMA) =
50/30 scattering particles thickness: 5 .mu.m (PMMA, primary
refractive index: 1.5 particle size 0.3 .mu.m) = 30/20/30
refractive index: 1.8 Auxiliary no no yes yes wiring Ag (100 nm) Ag
(100 nm) formed by photo- formed by photo- lithography (squared
lithography (squared cross section) cross section) Planarization
refractive index control no refractive index control no layer
particles (TiO.sub.2)/resin = particles (TiO.sub.2)/resin = 25/75
25/75 thickness: 6 .mu.m thickness: 6 .mu.m refractive index: 1.756
refractive index: 1.756 Diffused Material of above no Material of
above no layer planarization layer/ planarization layer/ light
scattering light scattering particles (PMMA) = particles (PMMA) =
50/50 50/50 thickness: 5 .mu.m thickness: 5 .mu.m Light 143% 155%
110% 157% extraction efficiency Comparative Ex. 5 Comparative Ex. 6
Comparative Ex. 7 Comparative Ex. 0 Organic EL yes yes yes yes
layer (HIL layer*.sup.1 (Al electrode) (Al electrode) (Al
electrode) thickness increase) (Al electrode) Conductive ITO (100
nm) coating-type diffused coating-type diffused ITO (100 nm) layer
(refractive index: conductive layer conductive layer (refractive
index: 2.0) (PEDOT-PSS)/ (PEDOT-PSS)/ 2.0) refractive index control
refractive index control particles (TiO.sub.2) = particles
(Al.sub.2O.sub.3)/light 30/20 scattering particles thickness: 5
.mu.m (PMMA, primary refractive index: 1.80 particle size 1.5
.mu.m) = 30/20/30 thickness: 5 .mu.m refractive index: 1.58
Auxiliary yes no no no wiring Ag (100 nm) (resist protected over
ITO) Planarization refractive index control no no no layer
particles (TiO.sub.2)/resin = 25/75 thickness: 6 .mu.m refractive
index: 1.756 Diffused Above material/light no no no layer
scattering particles (PMMA) = 50/50 thickness: 5 .mu.m Light 157%
158% 158% 100% (standard) extraction efficiency .sup.*1HIL layer:
hole injection layer
[0304] It was found from the results in Tables 1 and 2 that each of
the organic electroluminescent elements of Working Examples 1 to 11
had high light extraction efficiency.
[0305] It was found from Working Example 4 that when the primary
particle size of the light scattering particles used in the
conductive layer of the present invention is within the range of
0.5 to 10 .mu.m, there will be a good balance between forward and
rearward scattering, and good diffusion will be obtained, and
consequently high light extraction efficiency is obtained.
[0306] It was found from Working Examples 5 to 8 that when the
conductive layer of the present invention is configured from two
layers, there is better flatness of the face on which the organic
layer is formed, which contributes to better performance of an
organic electroluminescent element that is susceptible to the
effect of unevenness of the film formation face, and consequently
high light extraction efficiency is obtained.
[0307] The organic electroluminescent element of Working Example 11
is an element in which refractive index control particles (ZnO)
with a refractive index of less than 2.0 were used. In this case,
the amount in which ZnO needs to be added to increase the
refractive index of the conductive layer is greater than when using
TiO.sub.2 or ZrO as the refractive index control particles. As a
result, with the organic electroluminescent element of Working
Example 11, there is more scattering caused by the ZnO added to the
conductive layer, and there is also more rearward scattering in the
conductive layer, and a slight decrease in light extraction
efficiency is noted as compared to Working Examples 1, 9, and
10.
[0308] In the organic electroluminescent element of Comparative
Example 1, ITO containing no light scattering particles is used as
the transparent electrode, and the light scattering particles are
contained in the planarization layer. It is thought that this
element has unevenness in the planarization layer, and a decrease
in light extraction efficiency attributable to electrical leakage
caused by the unevenness was noted.
[0309] In the organic electroluminescent element of Comparative
Example 2, there was noted a decrease in light extraction
efficiency attributable to the fact that the primary particle size
of the light scattering particles contained in the conductive layer
was only 0.3 .mu.m.
[0310] In the organic electroluminescent element of Comparative
Example 3, there was noted a further decrease in extraction
efficiency attributable to the fact that the electrical leakage
caused by unevenness in Comparative Example 1 was exacerbated by
auxiliary wiring.
[0311] In the organic electroluminescent elements of Comparative
Examples 4 and 7, there was noted a decrease in light extraction
efficiency attributable to the fact that the refractive index of
the conductive layer was lower than that of the organic
light-emitting layer.
[0312] In the organic electroluminescent element of Comparative
Example 5, there was noted a decrease in light extraction
efficiency attributable to the fact that the auxiliary wiring was
coated with a resist, which increased the thickness of the hole
injection layer.
[0313] In the organic electroluminescent element of Comparative
Example 6, there was noted a decrease in light extraction
efficiency attributable to the fact that the conductive layer
contained no light scattering particles, and the ability of the
conductive layer to convert the optical angle was extremely
low.
INDUSTRIAL APPLICABILITY
[0314] The organic electroluminescent element of the present
invention can be used favorably in a variety of fields, such as
various kinds of lighting, computers, onboard displays, outdoor
displays, household devices, commercial devices, consumer devices,
traffic displays, clock and watch displays, calendar displays,
luminescent screens, and acoustic devices.
DESCRIPTION OF SYMBOLS
[0315] 1 glass substrate [0316] 2 coating-type diffused conductive
layer [0317] 3 coating-type diffused conductive layer 1 [0318] 4
coating-type diffused conductive layer 2 [0319] 5 organic layer
[0320] 6 reflecting electrode [0321] 7 auxiliary wiring [0322] 8
sealing can [0323] 9 diffused layer [0324] 10 planarization layer
[0325] 11 transparent electrode (ITO) [0326] 12 coating-type
conductive layer (containing no refractive index control particles)
[0327] 13 resist
* * * * *